Known cling-fastener parts are produced from thermoplastic polyolefins by extrusion. The thermoplastic material, in the plastic or liquid state, is fed, for example, to a gap between a pressure roll and a shaping roll. The shaping roll has a large number of radial cutouts, with both of its ends being open. The thermoplastic material penetrates into the cutouts under the action of the nip pressure, and substantially cures, such that the cling-fastener parts, in the form of a three-dimensional structure, can be released from the shaping roll. The cling-fastener base is molded in the gap between the shaping roll and the pressure roll. The base and the interlocking means, specifically the interlock projections formed in the cutouts and the interlock tips formed, are one single bonded piece.
The materials preferably used in the conventional processes are thermoplastics such as polypropylene, polyamide or polyethylene.
An example of this process is disclosed in WO 98/20767.
High nip pressures of from about 500 N/m to some thousands of N/m are required to achieve adequate supply of the plastic material, in its plastic or liquid state, to the cutouts.
In addition, the relatively low cooling rate of the thermoplastic polymers means that only small meterages of the three-dimensional cling-fastener sheeting can be produced on a shaping roll having a width of about 400 mm.
Production of cling-fastener parts via extrusion of thermoplastics requires a considerable energy cost to heat the thermoplastic composition to temperatures as high as 300° C.
The known processes place production-related restrictions on both the maximum width of the web of cling-fastener sheet and the minimum thickness of the cling-fastener sheet. Velcro Industrie B.V. developed longitudinal and/or transverse stretching processes, described in PCT WO 98/32349, for producing wider, and very thin, film-type cling-fastener sheets. A disadvantage with this process, besides the large amount of high-cost resource used for production, is that each stretching process markedly reduces the number of interlocking means per unit of area.
U.S. Pat. No. 5,787,784 discloses a process for producing cling-fastener parts, by compression molding a thermoplastic material into the shape of a large number of interlocking means. The patent also teaches that the cling-fastener parts may be produced form thermosets.